Process for eliminating organic matter and for generating energy

ABSTRACT

Process for destroying organic matter, in which said organic matter in ground form is introduced into a reactor and subjected to flameless combustion at a temperature of 240 to 400° C. under a pressure of 100 to 300 bar, in the presence of an oxygen-containing oxidizer for at least 20 minutes, while stirring the medium, and process for generating energy, in which the energy generated by the combustion is furthermore recovered.

The subject of the present invention is a novel process for the disposalof organic matter and production of energy

In present-day society, the disposal of waste and in particular oforganic matter especially of animal origin is becoming increasinglyimportant.

Moreover, the appearance of certain disease factors such as prionsnecessitate a radical destruction of much organic matter.

The waste to de disposed of can be solid, or non-solid.

It is already known, for example, to dispose of some waste by pyrolysis,i.e. by combustion at high temperature in a furnace.

As regards more particularly, for example, animal carcasses, the rawproduct is firstly converted into a solid waste called animal meal,which is then destroyed by incineration, i.e. by combustion with a flameat a temperature above 850° C.

But incineration produces dioxins, and it must be carried out on mealwhich produces dusts which may be toxic.

It would therefore be desirable to find an effective technique for thedisposal of organic matter, making it possible to work directly on theraw product, not producing toxins and making it possible to avoid theformation of potentially toxic dusts.

It would be also be desirable to find a process which does not requireenergy and which even, if possible, produces energy rather thanconsuming it.

After a lengthy search, the applicants have found a satisfactoryprocess.

This process is essentially based on a low-temperature combustionwithout flame at a relatively low temperature, and under pressure, inthe presence of a fuel such as air.

For this reason, the subject of the present application is a process forthe destruction of organic matter, in which the said matter isintroduced in ground form into a reactor and subjected to combustionwithout flame at a temperature of 240 to 400° C., under a pressure of100 to 300 bars, in the presence of an oxygenated fuel, for at least 20minutes, while stirring the medium.

By “organic matter” is meant carbon-containing matter originating fromanimal or vegetable entities, whether living or not. More specifically,it is matter capable of decomposing. This concept must not be confusedwith that of “organic compound”, a family to which, in particular,plastics and polymers belong and, more particularly, PCBs(polychlorinated biphenyls), also called, in particular in Quebec, BPCs(Biphenyles PolyChlorés) as well as polychloroterphenyls, monomethyltetrachlorodiphenylmethane, monomethyl dichlorodiphenylmethane andmonomethyl dibromodiphenylmethane which are treated in the same way asthem.

According to the present invention, the treated organic matter need notbe in solid form. It can clearly be in a form capable of being ground(i.e. chopped in the case of meat or fish for example).

Under preferred conditions of implementation of the invention, rawproducts are processed. In particular they are not trimmed.

As organic matter, there may be mentioned that of animal origin(including human) in particular animal by-products including poultrybreeding and fishery by-products and animal waste.

There may be mentioned in particular organic matter of animal originsuch as that from bovines, porcines, caprines, poultry, equids, rodentssuch as rabbits and hares. There may also be mentioned in particularwaste leaving animal abattoirs or quartering plants, for examplecarcasses of cattle, poultry, pigs, sheep, and animal fats originatingfrom the preparation of meats. Liquid manures and fishery waste may alsobe mentioned.

Some of this matter may be in the form of cadavers or carcasses. It mayalso comprise animal parts such as the blood, feet, head, horns, muzzle,tonsils/pharyngeal lymphatic ring, penis, tail, lungs, kidneys,oesophagus, liver, heart, diaphragm, spleen, forestomachs, stomach,testicles, trachea, larynx, extralobular bronchi, biliary vesicle, bile,fat, intestine, mesentery, anus, female genitalia, udders, foetuses,spinal cord and dura mater, vertebral column, sacrum, tendons,ligaments, nervous tissue, lymphatic tissue, blood vessels, meat notintended to be used as food. It can also comprise metabolic waste.

There may also be mentioned waste of any kind originating from thepharmaceutical industry or hospitals or veterinary hospitals for examplesuch as dirty cottons, linen or compresses, anatomical waste of human oranimal origin such as those mentioned above.

There may also be mentioned in particular organic matter suspended ordissolved in waste (also called residual) or washing water. Domesticwaste water consists of effluent flushed from toilets, household waterdrained from kitchens and bathrooms. The waste present in this dirtywater is constituted by degradable organic matter and mineral matter.These substances are dissolved or suspended. For the record, waste watersystems discharge into treatment plants where the water is processed andwhere most of the organic matter is in the form of sludges.

Primary sludges, deposits recovered by simple decantation of waste waterand displaying high concentrations of mineral matter (sand, soil etc.)but also organic matter, can be treated just as well as physico-chemicalsludges, sludges which resemble primary sludges but to which a reagenthas been added (salts of iron, aluminium, or other flocculating agents)in order to agglomerate the fine particles and improve the decantation,as biological sludges, also called secondary sludges, and originate froma biological purification of the water (activated sludges, bacterialbeds etc.). There may also be mentioned the mixed sludges constituted bya mixture of primary and biological sludges and extended aerationsludges obtained without primary decantation with intensively aeratedpollutants.

There may also be mentioned animal by-products not intended for humanconsumption in categories 1 2 and 3 according to the regulation of 3Oct. 2002 setting out in France the health rules applicable to animalby-products not intended for human consumption.

Under preferred conditions of implementation of the invention, the wasteis used in the process in reduced form.

By “reduced form” is meant that the pieces of organic matter orcontaining organic matter are small in size. They are present forexample in the form of a pasty slurry. The grain size of at leastadvantageously 50%, preferably 80%, in particular 90% of the pieces isadvantageously less than 20 mm, preferably less than 15 mm, inparticular less than 10 mm, quite particularly less than 5 mm(evaluation by screening).

It is advantageous to work on a slurry of the organic matter that it iswished to treat.

The state of the products (solid, slurry, etc.) is indicated in astandard fashion for normal conditions of temperature and pressure.

The process of the invention can be implemented between 240 and 400° C.,preferably between 250 and 350° C., particularly between 280 and 320° C.

The process of the invention is implemented under a pressure of 100 to300 bars, preferably between 150 and 250 bars, preferably between 180and 230 bars, particularly approximately 200 bars.

Oxygenated compounds may be mentioned as fuel.

Under preferred conditions of implementation of the invention, oxygen isused, in particular in the form of air optionally mixed with one or moreother gases.

Under further other preferred conditions of implementation, oxygenatedcompounds originating from industrial waste or by-products, such as forexample nitrogen (II) oxide, are used.

It is advantageous to work in the presence of an excess of fuel.

To this end, the chemical oxygen demand (COD) of the organic matter itis wished to treat can be determined beforehand. For the record, the CODexpresses the quantity of oxygen necessary to oxidize the organic matter(biodegradable or not) using an oxidant, potassium bichromate.

Under further other preferred conditions of implementation of theinvention, operations take place in the presence of a catalyst, inparticular based on Cu, Pt, Pd, Ru, Rh, Ti, in particular on differentsupports such as oxides of aluminium, cerium or silicon.

The catalyst will be for example a metallic oxide, such as the oxide ofselenium, rhenium or hafnium, or those mentioned in the examples.

The catalyst can be for example used at a rate of approximately 2 g/L.

It can in particular be used at a pH of approximately 12.

Under further other preferred conditions, a zeolite will be used.

The reaction time depends on the quantity of organic matter introducedat the start. The reaction time can vary between 20 min. and 120 min.for carbon concentrations comprised between 5 g and 40 g per litre,advantageously 20 to 120 min, preferably 60 to 100 min, quiteparticularly 75 to 90 min.

As the process of the invention is autothermal, the initial heating canbe discontinued as soon as the set temperature is reached.

Under other preferred conditions of implementation of the invention, oneor more input effluents are heated, for example, the fuel or thesupplementary organic matter to be treated in the case ofsemi-continuous, or continuous, implementation using the energy producedby the implementation of the process.

Under further preferred conditions of implementation of the invention,the heat energy produced by the reaction is removed using an aqueousfluid in particular, such as using industrial effluents, and moreparticularly using effluents from slaughterhouses for on-site treatmentof the raw animal matter.

The stirring system can be a standard bladed system. Under preferredconditions of implementation, the fuel, preferably air, performs or inparticular contributes to the stirring of the treated organic matter.

In order to do this, it is advantageously injected under pressure withinthe organic matter.

The process of the invention can be implemented non-continuously,semi-continuously, or continuously. The reactor will be suited to theform of implementation of the process. This is generally any suitableenclosure capable of withstanding high temperature and pressure.

At the end of the implementation of the process, an aqueous suspensioncontaining essentially minerals is obtained.

The latter can, depending on its composition, be retreated or discardeddirectly into the natural environment or transferred to a treatmentplant.

The mineral phase is a final waste.

The process of the invention has remarkable qualities. It allows theeffective destruction of the treated organic matter, in particularproteins, and quite particularly prions.

II allows this organic matter to be converted essentially into minerals,water and carbon dioxide.

The process also offers the advantage of being autothermal. When thecombustion is started, it is no longer necessary to supply additionalenergy.

Excess energy is actually obtained, which for example allows the heatingof the input effluents for example the fuel or additional organic matterto be treated. The effluents are preferably brought to the reactiontemperature.

The quantity of water necessary to remove the heat energy produced bythe reaction can be provided by industrial effluents, and moreparticularly effluents from slaughterhouses for on-site treatment of theraw animal matter. This produced energy can also be used to supplement adistrict heating system.

The process allows operation not only on animal meal, as is the casewith incinerators, but also on raw products.

The invention can be implemented simply in a reactor capable ofwithstanding the above pressures, for example by using a reactor fittedwith a heating system, a system for introducing fuel, a system forintroducing organic matter, a stirring system, a gas-evacuation system,a bottom outlet for the mineral matter, and preferably water and bathprobes.

The above properties are illustrated below in the experimental part.They justify the use of the processes described above in the productionof energy.

For this reason a subject of the present application is also a processfor the production of energy in which organic matter is introduced inground form into a reactor and subjected to combustion without flame ata temperature of 240 to 400° C., under a pressure of 100 to 300 bars, inthe presence of an oxygenated fuel, for at least 20 minutes, whilestirring the medium and the energy produced by the combustion isrecovered.

The recovery of the energy produced by the combustion can be achieved inparticular by the use of one or more heat exchangers, in particularexchangers with brazed plates and fins.

The energy thus produced and recovered for example in the form of hotliquid, for example hot water, can be used in a standard fashion.

The preferred conditions of implementation of the processes describedabove for the destruction of organic matter also apply to the othersubjects of the invention mentioned above, in particular to theprocesses for the production of energy.

FIG. 1 describes a type of apparatus and assembly that can be used toimplement the invention, used for the realization of the followingexamples which illustrate the present application.

EXAMPLE 1 Treatment of a batch of raw animal matter

A batch (batch system) of 20 grams of substrate is introduced into a hotoxidation treatment reactor, and hermetically sealed.

The hot oxidation treatment reactor used is an autoclave with an workingcapacity of 450 mL formed from a stainless steel crucible and a covermade of Hastelloy C276, operating sub-critically. The apparatus isdesigned to withstand a maximum temperature of 400° C. and a maximumpressure of 30 MPa. The reactor is heated by an electric furnace with anoutput of 4500W, placed around the autoclave. The system is also fittedwith a mechanical stirrer and a manometer. The safety of the whole isensured by a solenoid valve and a bursting disk. The reactor also hastwo liquid and gaseous feed/offtake lines.

The treated substrate is constituted by 20 g of raw animal matter (8 gdry weight), not trimmed, in the form of a brown pasty slurry with acharacteristic odour and a grain size of less than 5 mm.

The composition of the samples that is given below was determinedrelative to the dry matter.

Average composition of the raw animal matter:

Elements (%) DM (%) TOC (%) C H N S Cl P 35-40% 60 56 8.7 5.3 0.48 0.371.83 DM = Dry Matter TOC = Total Organic Carbon

Mechanical stirring is maintained continuously at 500 rpm. The furnaceis then started and the thermostat adjusted so as to reach a temperatureof 280° C. inside the reactor.

At the set temperature, air is injected and the pressure is set at 200bars. The thermostat stops. A continuous flow of air is provided bymeans of a microleak at the outlet of the reactor. This is allowed toreact for 60 min.

The heat energy produced by the reaction is removed using water.

The optimum hydrothermal oxidation reaction produces a liquid effluent.This effluent contains 1.6 g/L of TOC (including 0.8 g of acetic acid)and 1.6 g/L of ammonia. The destruction of the organic matter representsa reduction of more than 99%.

At end of the reaction, the solid phase contains approximately 400 mg ofinert mineral matter, which represents a 95% reduction of the drymatter. This solid phase contains a negligible quantity of organicmatter.

The gaseous effluents produced are separated and collected using acondenser then trapped in an acid (HCl) then a basic (NaOH) solution.

EXAMPLE 2 Treatment of Raw Animal Matter

The procedure is as given above in Example 1, but adding 2 g/L platinumcatalyst on alumina at pH 12. The TOC value of the output effluent isnot more than 60 mg/L.

EXAMPLE 3 Treatment of Raw Animal Matter

The procedure is as given above in Example 1, but adding 2 g/L platinumcatalyst on alumina at pH 12. The value of the concentration of ammoniais not more than 32 mg/L.

For the three examples, it was not possible to detect the presence ofproteins in the final medium by the determination technique used. Theprocess of the invention is therefore effective in disposing inparticular of prions, both in organic matter and in animal meal.

1. A process for the destruction of organic matter, in which the saidmatter is introduced in ground form into a reactor and subjected tocombustion without flame at a temperature of 240 to 400° C., under apressure of 100 to 300 bars, in the presence of an oxygenated fuel, forat least 20 minutes, while stirring the medium.
 2. A process accordingto claim 1, characterized in that the organic matter is of animalorigin.
 3. A process according to claim 1, characterized in that theorganic matter is an organic matter originating from cells suspended ordissolved in waste water (residual water).
 4. A process according toclaim 1, characterized in that the grain size of at least 50% of thepieces of the organic matter is less than 20 mm.
 5. A process accordingto claim 1, characterized in that it is implemented between 250 and 350°C.
 6. A process according to claim 1, characterized in that it isimplemented between 150 and 250 bars.
 7. A process according to claim 1,characterized in that the oxygenated fuel comprises air.
 8. A processaccording to claim 1, characterized in that it is implemented in thepresence of an excess of fuel.
 9. A process according to claim 1,characterized in that it is implemented in the presence of a catalyst,for example based on Cu, Pt, Pd, Ru, Rh, Ti.
 10. A process according toclaim 1, characterized in that one or more input effluents are heated,for example the fuel or the supplementary organic matter to be treatedin the case of semi-continuous, or continuous, using the energy producedby the implementation of the process.
 11. A process according to claim1, characterized in that the fuel is injected under pressure within theorganic matter in order to stir it.
 12. A process for the production ofenergy in which an organic matter is introduced in ground form into areactor, subjected to combustion without flame as defined in one ofclaims 1 to 11 and the energy produced by the combustion is recovered.